New Scientist Live

Climate myths: They predicted global cooling in the 1970s

Indeed they did. At least, a handful of scientific papers discussed the possibility of a new ice age at some point in the future, leading to some pretty sensational media coverage (see Histories&colon; The ice age that never was).

One of the sources of this idea may have been a 1971 paper by Stephen Schneider, then a climate researcher at NASA’s Goddard Space Flight Center in Maryland, US. Schneider’s paper suggested that the cooling effect of dirty air could outweigh the warming effect of carbon dioxide, potentially leading to an ice age if aerosol pollution quadrupled.

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However, Schneider soon realised he had overestimated the cooling effect of aerosol pollution and underestimated the effect of CO2, meaning warming was more likely than cooling in the long run. In his review of a 1977 book called The Weather Conspiracy&colon; The Coming of the New Ice Age, Schneider stated&colon; “We just don’t know…at this stage whether we are in for warming or cooling – or when.” A 1975 report (pdf format) by the US National Academy of Sciences merely called for more research.

The calls for action to prevent further human-induced global warming, by contrast, are based on an enormous body of research by thousands of scientists over more than a century that has been subjected to intense – and sometimes ferocious – scrutiny. According to the latest IPCC report, it is more than 90% certain that the world is already warming as a result of human activity (see Blame for global warming placed firmly on humankind).

Update&colon; A survey of the scientific literature has found that between 1965 and 1979, 44 scientific papers predicted warming, 20 were neutral and just 7 predicted cooling. So while predictions of cooling got more media attention, the majority of scientists were predicting warming even then.